Optical waveguide transmitter-receiver module

ABSTRACT

A planar-mounted optical waveguide transmitter-receiver module has a plurality of separated silicon substrates and a PLC substrate hybrid-integrated. In this module, electrical crosstalk between the light emitting element side and photo-receiving element side is reduced, and an adhesion area between substrates is decreased. In this module, a first silicon substrate, on which are mounted a light emitting element and photo-receiving element, is positioned opposing a second silicon substrate, in which is formed a V groove, in which an optical fiber is to be inserted and fixed in place with resin or by other means. On joining surfaces of the first silicon substrate and joining surfaces of the second silicon substrate are positioned and fixed in place joining surfaces on the back face of the optical waveguide (PLC) substrate, in which is formed an optical waveguide. By this means, the light emitting element, the photo-receiving element, and the optical fiber inserted into the V groove are optically aligned with and simultaneously optically coupled with the optical waveguide of the PLC substrate.

This is a Continuation-In-Part of parent application Ser. No.09/818,894, filed Mar. 28, 2001, now U.S. Pat. No. 6,456,767.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention concerns a planar-mounted optical waveguidetransmitter-receiver module, in which silicon or other substrates,separated into a plurality of substrates, and an optical waveguide(planar lightwave circuit) substrate (hereafter “PLC substrate”), arehybrid-integrated.

2. Description of Related Art

Optical terminal devices for use in optical subscriber systems aresubjected to such demands as smaller integration sizes,multi-functionality, and reduced prices. Optical modules with opticalwaveguides as devices effective for satisfying such demands are cominginto widespread use. Conventional silicon platform structures, in whichoptical waveguides and silicon substrates are united, have problemswhich include complexity of manufacturing processes and limitations onthe manufactured quantity per unit wafer. For this reason, variousplanar-mounted optical waveguide transmitter-receiver modules in which asilicon substrate and a PLC substrate are hybrid-integrated have beenproposed. Below, the structure of conventional optical waveguidetransmitter-receiver modules is explained, referring to FIGS. 1 through3.

FIG. 1 is a perspective view of an optical waveguidetransmitter-receiver module, representing conventionalsynchronous-transfer mode passive optical networks (hereafter “STM-PON”)and π-PON systems.

This optical waveguide transmitter-receiver module has a siliconsubstrate 1, and an optical waveguide layer 2 is formed on this siliconsubstrate 1. The optical waveguide layer 2 is formed by, for example,deposition of quartz glass by sputtering methods and execution ofvitrification processing of this deposited layer by means ofhigh-temperature annealing. In this way, the optical waveguide layer 2and silicon substrate 1 are formed as a unit to constitute the siliconplatform substrate. A dual-branching optical waveguide 3 is formedwithin the optical waveguide layer 2 for use in bidirectionalcommunication. The optical waveguide 3 has entry and exit end faces 3 ato 3 d. A groove is cut in the branch part 3 e, and awavelength-selection filter embedded therein. The device with thisfilter 4 removed is a π-PON device.

On the silicon substrate 1, a semiconductor laser or other lightemitting element 5 and photodiode or other photo-receiving element 6 arefixed in place, by soldering or other means, to oppose the end faces 3a, 3 b of the optical waveguide. The module is designed to enable theconnection of optical fibers to the end faces 3 c, 3 d of the opticalwaveguide 3 by means of optical connectors.

For example, in an optical waveguide transmitter-receiver module for usein STM-PON systems, a light emitting element 5 and photo-receivingelement 6 operate at different times (with different timing). When thelight emitting element 5 operates, light is emitted from this lightemitting element 5, and this light is incident on the end face 3 a ofthe optical waveguide 3. Light incident on the end face 3 a istransmitted within the optical waveguide 3, is wavelength-selected bythe filter 4 provided at the branch part 3 e, and is, for example,emitted from the end face 3 c and sent to an optical fiber via anoptical connector. On the other hand, light sent from an optical fiberis incident on, for example, the end face 3 c via an optical connector.The incident light is wavelength-selected by the filter 4, and emittedfrom the end face 3 b. The emitted light is received by thephoto-receiving element 6, converted into an electrical signal, andoutput. Light of different wavelengths sent from an optical fiber, afterincidence on the end face 3 c, is wavelength-selected by the filter 4and emitted from the end face 3 d.

FIG. 2 is a perspective view of an optical waveguidetransmitter-receiver module compatible with a conventionalasynchronous-transfer mode passive optical network (asynchronoustransfer mode PON, hereafter “ATM-PON” systems).

This optical waveguide transmitter-receiver module for ATM-PON systemshas nearly the same optical component configuration as in FIG. 1, butthe shape of the optical waveguide 3A formed within the opticalwaveguide layer 2, and the fixed positions of the emissive element 5 andphoto-receiving element 6, are different from those of FIG. 1. That is,on a silicon platform substrate in which the optical waveguide 3A andsilicon substrate 1 are formed integrally, entry/exit end faces 3 b to 3d are formed in the optical waveguide 3A. The photo-receiving element 6is fixed in place opposing the end face 3 b on the silicon substrate 1,by soldering or other means, and the light emitting element 5 is fixedin place on the silicon substrate 1 opposing the end face 3 d, distantfrom the other end face, by soldering or other means. The module isdesigned such that an optical fiber can be connected, by means of anoptical connector, to the end face 3 c.

In this optical waveguide transmitter-receiver module for ATM-PONsystems, the light emitting element 5 and photo-receiving element 6operate simultaneously. Consequently, resistance to crosstalk betweenoptical transmission and reception signals is required. For this reason,the light emitting element 5 and photo-receiving element 6 are mountedon the silicon substrate as far apart as possible, and by this means,the adverse effects of electrical crosstalk induced by electromagneticcoupling via the silicon substrate between the light emitting element 5and photo-receiving element 6 are reduced.

FIG. 3 is a perspective view of a conventional optical waveguidetransmitter-receiver module for π-PON systems, with hybrid-integrationof silicon substrate and PLC substrate.

This optical waveguide transmitter-receiver module for π-PON systems hasa silicon substrate 7 with flat surface. On the flat surface of thissilicon substrate 7 is formed by etching a V-shaped etched groove(hereafter “V groove”) 8, for aligned mounting of an optical fiber. Alight emitting element 5 and photo-receiving element 6 are fixed inplace on the silicon substrate by soldering or other means. A PLCsubstrate 9, manufactured in advance, is fixed in place by resin,soldering or other means on the silicon substrate 7, opposing the lightemitting element 5, photo-receiving element 6, and V groove 8. The PLCsubstrate 9 is formed by layered deposition of an optical circuit, toserve as the optical waveguide 3B, on parent-material or matrixsubstrate, primarily silicon, quartz, or a polyimide. The opticalwaveguide 3B is provided with entry/exit end faces 3 a to 3 c opposingthe light emitting element 5, photo-receiving element 6, and V groove 8.

In this optical waveguide transmitter-receiver module for π-PON systems,an optical fiber is inserted into the V groove 8, and is bonded using aresin. For example, light emitted from the light emitting element 5 isincident on the end face 3 a of the optical waveguide 3B. The incidentlight passes through the branch part 3 e, is emitted from the end face 3c, and is sent to the optical fiber in the V groove 8. On the otherhand, light sent from the optical fiber is incident on the end face 3 cof the optical waveguide 3B. The incident light passes through thebranch part 3 e, and is emitted from the end face 3 b. The emitted lightis received by the photo-receiving element 6, and is converted into anelectrical signal and output.

However, the conventional optical waveguide transmitter-receiver modulesof FIGS. 1 to 3 have the following problems (1) to (3).

(1) Case of the optical waveguide transmitter-receiver module structureof FIG. 1 and FIG. 2

An optical waveguide transmitter-receiver module such as that of FIG. 1and FIG. 2 adopts a silicon platform structure, in which the opticalwaveguide 3, 3A and silicon substrate 1 are integrated. That is,numerous optical waveguide transmitter-receiver module areas areprovided on a silicon wafer, for example, and wiring patterns and otherelectrical circuit parts are formed in each of these areas on thesilicon substrate 1. At the same time, quartz glass or other material isdeposited by sputtering methods to form the optical waveguide layer 2,and thereafter a light emitting element 5 and photo-receiving element 6are fixed in place on the silicon substrate 1 by soldering or othermeans. Consequently the manufacturing process is complex, and moreovereach optical waveguide transmitter-receiver module area formed on thewafer must be made slightly larger in order to expedite manufacturingprocesses. Hence such problems as limits on the quantity manufacturedper unit wafer arise.

Moreover, in manufacturing processes for optical waveguide layers 2,high-temperature annealing processing must be used to executevitrification of quartz waveguide crystals. However, if suchhigh-temperature annealing is performed, defects occur in the siliconcrystal of the silicon substrate 1, so that highly precise formation ofthe V groove by etching is made difficult, and consequently therealization of a receptacle structure (an optical connector structurehaving a function for optical fiber attachment and removal) becomesdifficult. Further, when connecting an optical fiber array to the endfaces 3 c, 3 d of the optical waveguide 3, 3A, optical core-alignedconnection in order to match the optical axes is essential; and for thisreason, connection tasks have required much care.

(2) Case of optical waveguide transmitter-receiver modules for ATM-PONsystems of FIG. 2

Since a light emitting element 5 and photo-receiving element 6 areoperated simultaneously, superior cross-talk performance is required forthe transmitting and receiving signals. Therefore, the decrease ofelectric cross-talk between the light emitting element 5 and thephoto-receiving element 6 mounted on the silicon substrate 1 must beattained by making the dimensions of the silicon substrate larger forincreasing the distance between the positions where the elements 5 and 6are mounted, and, for this reason, the module becomes large.

(3) Case of optical waveguide transmitter-receiver modules for π-PONsystems of FIG. 3

In these optical waveguide transmitter-receiver modules for π-PONsystems, the silicon substrate 7 and PLC substrate 9 are manufacturedseparately and independently, so that manufacturing processes can besimplified, and manufacturing quantities per unit wafer can beincreased. Further, the V groove 8 is formed in integral fashion on thesilicon substrate 7, so that by inserting an optical fiber into this Vgroove 8 and bonding with resin, the optical axes of this optical fiberand the end face 3 c of the optical waveguide 3B are aligned;consequently optically non-aligned mounting of the optical fiber ispossible. However, even in the case of this optical waveguidetransmitter-receiver module for π-PON systems, as with (2) above, whenusing this model in an ATM-PON system, the dimensions of the siliconsubstrate 7 must be made large in order to secure resistance toelectrical crosstalk over the silicon substrate 7 between the lightemitting element 5 and photo-receiving element 6. Further, it isstructurally difficult to insert the wavelength-selection filter 4 intothe PLC substrate 9, and so there is the added problem that versatilityof support for STM and ATM is lacking.

SUMMARY OF THE INVENTION

One object of this invention is to provide an optical waveguidetransmitter-receiver module which, by reducing electrical crosstalk, canbe made smaller and can be mass-produced.

A second object of this invention is to provide an optical waveguidetransmitter-receiver module which, by decreasing the bonding area withthe substrate, reduces the occurrence of malfunctions.

A third object of this invention is to provide an optical waveguidetransmitter-receiver module comprising a mechanism to prevent influx ofthe adhesive used for improved manufacturing yields.

In order to resolve the above problems, this invention comprises theconfigurations described below. This invention concerns a planar-mountedoptical waveguide transmitter-receiver module hybrid-integrated onto aplurality of separated substrates. This module comprises a first siliconor other substrate, in the flat surface of which a first groove toaccommodate protrusions is formed, and in the flat surface of which afirst mark for position alignment is formed; a second silicon or othersubstrate, having the same thickness as this first substrate, in theflat surface of which is formed a second groove to accommodate aprotruding part and a third groove to accommodate an optical fiber, andin the flat surface of which a second mark for position alignment isformed; a semiconductor laser or other light emitting element, fixed inplace with position aligned with the surface of either the first or thesecond substrate; a photodiode or other optical photo-receiving element;and a PCL substrate or other third substrate.

In the case of a configuration in which the photo-receiving element isused in modes in which it operates simultaneously with the lightemitting element, the photo-receiving element is fixed in place, withits position aligned, on the surface of either the second or the firstsubstrate, whichever is not the substrate on which the light emittingelement is fixed in place. Further, when employing a configuration usedin modes in which the photo-receiving element and the light emittingelement operate at different times, the photo-receiving element is fixedin place, with its position aligned, on the first or the secondsubstrate, either the same substrate on which the light emitting elementis fixed, or the other substrate. In the third substrate is formed aprotrusion, of the thickness of the optical waveguide, electrodes andother components, in a position to oppose the first and second groovesand with back surface opposing the first and second substrates. In thethird substrate are also formed, at positions on side faces thereof andopposing the emitting part of the light emitting element and thereceiving part of the photo-receiving element, respectively, an entryend face and exit end face for the optical waveguide. Further, parts ofthe back surface of this third substrate are fixed or bonded to parts ofthe surfaces of the first and second substrates, with positions alignedusing the first and second marks as references.

By adopting such a configuration, in the case of an optical waveguidetransmitter-receiver module for ATM-PON systems in which the lightemitting element and photo-receiving element operate simultaneously, thelight emitting element and photo-receiving element are fixed in place,by soldering or other means, to different substrates, so that electricalcrosstalk via substrate between the light emitting element andphoto-receiving element is simply and appropriately reduced.

In the case of an optical waveguide transmitter-receiver module forSTM-PON systems or for π-PON systems in which the light emitting elementand photo-receiving element operate at different times, the problem ofelectrical crosstalk does not often occur, and so the light emittingelement and photo-receiving element are fixed in place, by soldering orother means, on the same substrate or on different substrates.

By means of a module of this invention, in the case of specifications inwhich both a light emitting element and a photo-receiving elementoperate simultaneously, by separating the substrate on which the lightemitting element is mounted and the substrate on which thephoto-receiving element is mounted, electrical crosstalk between thelight emitting element and the photo-receiving element can be simply andappropriately reduced. By this means, the dimensions of substrates onwhich light emitting element and photo-receiving elements are mountedcan be decreased, and the number of units manufactured from a wafer orsimilar can be increased. Further, in this configuration parts of afirst and second substrate are fixed to parts of a third substrate, sothat the adhesive areas between substrates can be decreased;consequently, warping of each substrate, strain arising from differencesin linear expansion coefficients, stress concentration, and degradationof bonding strength can be reduced.

In a preferred embodiment of this invention, dicing is used to formdicing grooves in the first and second groove sides, opposing the end ofthe third groove, the emitting part of the light emitting element andreceiving part of the photo-receiving element, respectively. By thismeans, when for example using adhesive to bond the first, second, andthird substrates, excess adhesive resin flows into the dicing grooves,and so prevents flow toward the light emitting element andphoto-receiving element.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the presentinvention will be better understood from the following description takenin connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of a conventional optical waveguidetransmitter-receiver module for use in STM-PON systems;

FIG. 2 is a perspective view of a conventional optical waveguidetransmitter-receiver module for use in ATM-PON systems;

FIG. 3 is a perspective view of a conventional optical waveguidetransmitter-receiver module for use in π-PON systems;

FIG. 4 is a perspective, exploded view of the optical waveguidetransmitter-receiver module of a first embodiment of this invention,applied to a π-PON system;

FIG. 5 is a perspective, exploded view of the optical waveguidetransmitter-receiver module of a second embodiment of this invention, asan example of application to an STM-PON system;

FIG. 6 is a perspective, exploded view of the optical waveguidetransmitter-receiver module of a third embodiment of this invention, asan example of application to an ATM-PON system;

FIG. 7 is a diagram explaining a method of position alignment of siliconsubstrates and PLC substrate in a fourth embodiment of this invention;

FIG. 8 is a diagram explaining a method of position alignment in a fifthembodiment of this invention;

FIG. 9 is a diagram explaining a method of position alignment of a sixthembodiment of this invention; and,

FIG. 10 is a diagram explaining a method of position alignment of aseventh embodiment of this invention.

FIG. 11 is a view of a first variation.

FIG. 12 is a view of another construction of the first variation.

FIG. 13 is a view of still another construction of the first variation.

FIG. 14 is a view of a second variation.

FIG. 15 is a view of a third variation.

FIG. 16 is a view of a fourth variation.

FIG. 17 is a view of a fifth variation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

FIG. 4 is a perspective, exploded view of the optical waveguidetransmitter-receiver module of a first embodiment of this invention,applicable to a π-PON system.

In this optical waveguide transmitter-receiver module, a strip orrectangle solid-shaped first substrate (for example, a siliconsubstrate) 10, on which are mounted optical elements, a strip orrectangle solid-shaped second substrate (for example, a siliconsubstrate) 20 having the same thickness as the silicon substrate 10, andfor connection of optical fibers; and a strip or rectangle solid-shapedthird substrate (for example, a PLC substrate) 30, on which is formed anoptical waveguide, are separated. These three substrates 10, 20, and 30are hybrid-integrated in a planar-mounted structure.

One of the principal surfaces of the silicon substrate 10, which is theupper face (hereafter simply “surface”), is flat, and in this surface,the first groove is formed (for example, an etched groove 11 is formedby etching). This first groove 11 is formed with a constant width, fromone side face of the first silicon substrate 10 to the other side face.Further, this first groove 11 is formed with a constant depth, in thedepth direction, from the flat surface of the silicon substrate 10. Theetched groove 11 is to accommodate the protruding part 33 on theback-face side of the PCL substrate 30, that is, the face on the sideopposing the first and second substrates 10, 20. The flat areas of thesilicon substrate surface in the vicinity of the etched groove 11,remaining after the etched groove 11 is formed, become the joiningsurfaces 14, 15 for fixing the PLC substrate 30. In this configurationexample, the joining surfaces 14, 15 are formed on either side of andenclosing the etched groove 11. A first dicing groove 16, adjoining andlinked with the etched groove 11, is formed by dicing. A wiring orinterconnection pattern is formed in the surface area of the siliconsubstrate 10 outside the grooves, adjoining the dicing groove 16. Ontothis wiring pattern, a semiconductor laser or other light emittingelement 18, and a photodiode or other photo-receiving element 19, areconnected by soldering or other means. When an electrical signal isapplied to the light emitting element 18, light is emitted from theactive layer or other emitting part 18 a. When light from outside isreceived by the receiving part 19 a of the photo-receiving element 19,this light is converted into an electrical signal and output.

The second substrate positioned opposing the silicon substrate 10,namely, the silicon substrate 20, has a smooth upper principal surface(hereafter simply “surface”). Second and third grooves are formed (forexample, etching is used to form an etched groove 21 and V groove 22) inthe flat surface of this second substrate 20. This second groove 21 is,like the first groove, formed in the second substrate 20 from one sideface on the side of the second silicon substrate 20 opposing the firstsubstrate 10. The second groove 21, which is an etched groove, is agroove which accommodates the protruding part 33 on the above-describedback-face side of the PCL substrate 30. The flat areas of the siliconsubstrate surface in the vicinity of the etched groove 21, remainingafter the etched groove 21 is formed, become the joining surfaces 24,25. The joining surfaces 24, 25 are surface areas for fixing in placethe PLC substrate 30. The third groove 22, which is a V groove, is agroove used for aligned mounting of an optical fiber; by inserting anoptical fiber into this groove and fixing it in place using resin orother material, the optical fiber is fixed in place with its opticalaxis aligned. Between the etched groove 21 and V groove 22 of the secondsilicon substrate 20, dicing is used to form a second dicing groove 26.

The PLC substrate 30 fixed on top of the silicon substrates 10, 20 has alayered structure in which a substrate of, for example, silicon, quartz,polyimide, or some other parent material, and an optical circuit toserve as the optical waveguide 31 on the parent-material or matrixsubstrate, are layered. The optical waveguide 31 has a dual-branchingstructure. This optical waveguide 31 has a structure in which a core foroptical transmission is formed at its center, and surrounding this acladding layer to envelop light is formed. The entry/exit end faces 31 ato 31 c of this optical waveguide 31 are formed on the side surfaces ofthe PLC substrate 30, and the end faces 31 a, 31 b are coupled to theend face 31 c by the branching part 31 e. The protruding part 33 of thecladding layer on the periphery of the optical waveguide core is formedprotruding on the back-face side of the PLC substrate 30. Flat places onthe back surface of the PLC substrate in the vicinity of this protrudingpart 33 serve as joining surfaces 34, 35. In this configuration example,these joining surfaces 34, 35 are formed on both sides of the protrudingpart. The joining surfaces 34, 35 are used for fixing to the joiningsurfaces 14, 15, 24, 25 of the first and second silicon substrates 10,20. This PLC substrate 30 is set such that the height from the joiningsurfaces 34, 35 to the optical waveguide core is the same as the heightof the emitting part 18 a of the light emitting element 18, thereceiving part 19 a of the photo-receiving element 19, and the opticalfiber core.

Such an optical waveguide transmission/receiving module may, forexample, be manufactured as follows.

In the wafer state, numerous chips for silicon substrate 10, chips forsilicon substrate 20, and chips for PLC substrate 30 are each formed,and dicing used to separate each of the chips. The silicon substrate 10and silicon substrate 20 are positioned opposing each other at aprescribed interval. That is, both the substrates 10 and 20 are providedin an arrangement with one side of each mutually opposed. On the joiningsurfaces 14, 15, 24, 25 of the surfaces of the silicon substrates 10,20, the protruding surfaces 34, 35 of the back surface of the PLCsubstrate 30 are placed, and these joining surfaces 14, 15, 24, 25 andjoining surfaces 34, 35 are bonded together with resin, solder, or bysimilar means, to fix the PLC substrate 30 in place on the siliconsubstrates 10, 20. Position adjustment in the X-Y directions isperformed by alignment referring to the images of metal or V groovemarks formed with high precision on each of the silicon substrates 10,20. By this means, the emitting part 18 a of the light emitting element18 and the end face 31 a of the optical waveguide 31 are opposed, thereceiving part 19 a of the photo-receiving element 19 and the end face31 b of the optical waveguide 31 are opposed, the end part of the Vgroove 22 and the end face 31 c of the optical waveguide 31 are opposed,and the substrates are fixed in place with these optical axes aligned.

An optical fiber is inserted and fixed in place, with resin or by othermeans, in the V groove 22 of an optical waveguide transmitter-receivermodule manufactured in this way. When the light emitting element 18 andreceiver element 19 are operated, light emitted from the emitting part18 a of the light emitting element 18 is incident on the end face 31 aof the optical waveguide 31. Light which has been incident passesthrough the branch part 31 e of the optical waveguide 31, is emittedfrom the end face 31 c, and is sent to the optical fiber in the V groove22. On the other hand, light sent from the optical fiber is incident onthe end face 31 c of the optical waveguide 31. Light which has beenincident passes through the branch part 31 e of the optical waveguide31, and is emitted from the end face 31 b. The emitted light is receivedat the receiving part 19 a of the photo-receiving element 19, isconverted into an electrical signal and output. In this way, throughsimultaneous optical coupling of the optical waveguide 31 and the lightemitting element 18, photo-receiving element 19 and optical fiber,transmitter-receiver module functions can be obtained.

This first embodiment has the following advantageous results (a) and(b).

(a) The silicon substrates 10, 20 and the PLC substrate 30 aremanufactured separately and independently, so that manufacturingprocesses can be simplified, and the quantities manufactured per unitwafer can be increased. Further, a V groove 22 is formed in the siliconsubstrate 20; by inserting an optical fiber into this V groove 22 andfixing it in place with resin or by other means, non-aligned mounting ofthe optical fiber can be realized.

(b) The silicon substrates 10, 20 and PLC substrate 30 are fixed inplace by means of these small-area joining surfaces 14, 15, 24, 25, 34,35, so that the bonding area can be reduced. As a result, warping ofeach of the substrates 10, 20, 30, strain arising from differences inlinear expansion coefficients, stress concentration, and degradation ofbonding strength can be reduced.

Second Embodiment

FIG. 5 is a perspective, exploded view of the optical waveguidetransmitter-receiver module of a second embodiment of this invention asan example of application to an STM-PON system. Components which arecommon with components in FIG. 4, showing the first embodiment, areassigned common symbols.

In the optical waveguide transmitter-receiver module of the secondembodiment, in addition to the V groove 22, another V groove 23 issimultaneously formed by etching in the silicon substrate 20 of FIG. 4.In this configuration example, the V grooves 22 and 23 are formed inparallel; but this does not limit the scope of this invention. Theoptical waveguide 31A formed in the PLC substrate 30 has entry/exit endfaces 31 a to 31 d; a groove is cut, for example by dicing, in thebranching part 31 e joining the end faces, and a wavelength-selectingfilter 32 is embedded. Otherwise the configuration is similar to that ofFIG. 4.

In the method of manufacture of this optical waveguidetransmitter-receiver module, the chip for the silicon substrate 10, thechip for the silicon substrate 20, and the chip for the PLC substrate 30are manufactured in advance. The joining surfaces 34, 35 of the PLCsubstrate 30 are placed on top of the joining surfaces 14, 15, 24, 25 ofthe silicon substrates 10, 20, and these joining surfaces 14, 15, 24,25, 34, 35 are bonded with resin, solder, or by other means.

In such an optical waveguide transmitter-receiver module, optical fibersare inserted into each of the V grooves 22, 23, and fixed in place withresin or by other means. When the light emitting element 18 andphoto-receiving element 19 are operated, for example, light emitted fromthe emitting part 18 a of the light emitting element 18 is incident onthe end face 31 a of the optical waveguide 31A. The incident light iswavelength-selected by a filter 32 for wavelength selection, provided atthe branch part 31 e of the optical waveguide 31A, and is emitted from,for example, the end face 31 c. The emitted light is sent to the opticalfiber inserted in the V groove 22. On the other hand, light sent fromthe optical fiber in the V groove 22 is incident on the end face 31 c ofthe optical waveguide 31A. The incident light is wavelength-selected bythe filter 32 for wavelength selection, and is, for example, emittedfrom the end face 31 b. The emitted light is received by the receivingpart 19 a of the photo-receiving element 19, is converted into anelectrical signal and output. Light of a different wavelength sent fromthe optical fiber in the V groove 22 is incident on the end face 31 c ofthe optical waveguide 31A. The incident light is wavelength-selected bythe filter 32 for wavelength selection, and emitted from the end face 31d. The emitted light is sent to the optical fiber inserted into the Vgroove 23.

In this way, a filter 32 for wavelength selection is inserted into thebranch part 31 e of the optical waveguide 31A, and so the module of thesecond embodiment is capable of bidirectional communications usingtwo-wavelength signals.

In the module of this second embodiment, advantageous results similar tothe results (a), (b) of the first embodiment are obtained, and inaddition the following result is obtained. Namely, in this module eachof the substrates 10, 20, 30 is separated, so that insertion of thefilter 32 for wavelength selection into the PLC substrate 30 is madeeasy.

Third Embodiment

FIG. 6 is a perspective, exploded view of the optical waveguidetransmitter-receiver module of a third embodiment of this invention, asan example of application to an ATM-PON system. Components which arecommon with components in FIG. 4 and FIG. 5, showing the first andsecond embodiments, are assigned common symbols.

For example, in the optical waveguide transmitter-receiver module usedin an ATM-PON system, the light emitting element 18 and photo-receivingelement 19 operate simultaneously, and electrical crosstalk occurs viathe silicon substrate between these elements, exerting adverse effects.Hence of the two separate first and second silicon substrates 10, 20,the photo-receiving element 19 is fixed in place by soldering or othermeans to the surface of the silicon substrate 10, and the light emittingelement 18 is fixed in place by soldering or other means to the surfaceof the other silicon substrate 20.

Simultaneously with formation of the V groove 22 for optical fiberinsertion, an etched groove 26 is formed in the vicinity of the V groove22 on the surface of the second silicon substrate 20. This groove 26prevents, for example, the influx toward the light emitting element 18of bonding resin when fixing the optical fiber in place in the V groove22. An optical waveguide 31B is formed in the PLC substrate 30 which isconnected on top of the silicon substrates 10, 20. The optical waveguide31B has entry/exit end faces 31 b to 31 d, and at the branch part 31 ewhich couples these, a groove is cut by dicing, for example, and awavelength-selection filter 32 is embedded.

In the method of manufacture of this optical waveguidetransmitter-receiver module, similarly to the first or the secondembodiments, the chip for the silicon substrate 10, the chip for thesilicon substrate 20, and the chip for the PLC substrate 30 aremanufactured in advance. The joining surfaces 34, 35 of the PLCsubstrate 30 are placed on top of the joining surfaces 14, 15, 24, 25 ofthe silicon substrates 10, 20, and these joining surfaces 14, 15, 24,25, 34, 35 are bonded with resin, solder, or by other means.

In an optical waveguide transmitter-receiver module manufactured in thisway, light emitted from, for example, a light emitting element 18 isincident on the end face 31 d of the optical waveguide 31B. The incidentlight is wavelength-selected by the filter 32 for wavelength selectionof the optical waveguide 31B, and is emitted from the end face 31 c. Theemitted light is sent to the optical fiber inserted in the V groove 22.On the other hand, light which is incident from the optical fiberinserted in the V groove 22 is incident on the end face 31 c of theoptical waveguide 31B. The incident light is wavelength-selected by thefilter 32 for wavelength selection, and is emitted from the end face 31b. The emitted light is received by the photo-receiving element 19, andconverted into an electrical signal.

In this way, by inserting a filter 32 for wavelength selection at thebranch part 31 e of the optical waveguide 31B, similarly to the moduleof FIG. 5, the module of this third embodiment is capable ofbidirectional communication using two-wavelength signals.

In addition to obtaining the advantageous results of the modules of thefirst and second embodiments, the module of this third embodiment alsoaffords the advantageous results (c) through (e) below.

(c) The silicon substrate 20 on which the light emitting element 18 ismounted and the silicon substrate 10 on which the photo-receivingelement is mounted are separated, so that electrical crosstalk viasilicon substrate between the light emitting element 18 andphoto-receiving element 19 can be greatly reduced. Moreover, there is noneed to increase the gap between the light emitting element 18 andphoto-receiving element 19 in order to reduce electrical crosstalk, asin conventional designs, so that the silicon substrates 10 and 20 can bereduced in size and placed in proximity. Hence the reduction in siliconsubstrate dimensions enables increases in quantities manufactured from awafer.

(d) An optical waveguide transmitter-receiver module like that of thisembodiment is, for example, fixed in place to a package or othermounting frame. When fixing the silicon substrates 10, 20 to a packageor other mounting frame, resin, solder, or some other means of bondingis used. In particular, if either an insulating sheet is providedbetween substrates and mounting frame, or insulating resin is used asthe adhesive, electrical crosstalk occurring via the mounting framebetween the light emitting element 18 and photo-receiving element 19 canbe further reduced. In order not to detract from the effect of heatdissipation from the silicon substrate 20, which is also a heat sink(heat-dissipating member) for the light emitting element 18, silverpaste or some other highly heat-conducting resin may be used as theadhesive between the mounting frame and the silicon substrate 20 onwhich the light emitting element 18 is mounted.

(e) As an advantageous effect included in the modules of the firstthrough third embodiments, by selecting a combination of the siliconsubstrates 10, 20 and PLC substrate 30 which are the principalcomponents, versatility in application to STM-PON systems, π-PONsystems, ATM-PON systems, and other systems is greatly enhanced, and agreater number of optical module manufacturing processes can beperformed in common.

In the first through third embodiments, an optical waveguidetransmitter-receiver module is formed by bonding together threeseparately fabricated substrates. In the first through thirdembodiments, by distributing the semiconductor among separatesubstrates, optical waveguide crosstalk can be reduced.

Fourth Embodiment

FIG. 7 is a diagram explaining a method of position alignment of siliconsubstrates and PLC substrate, showing a fourth embodiment of thisinvention.

FIG. 7 shows position alignment marks within joining x-y surfaces of thefirst and second silicon substrates 10, 20 and the PLC substrate 30,which is the third substrate, used in the manufacture of, for example,the optical waveguide transmitter-receiver module of FIG. 4, showing thefirst embodiment of this invention.

For example, first positioning marks 41-1, 41-2 are formed on thejoining surfaces 14, 15 of the silicon substrate 10; and secondpositioning marks 41-3, 41-4 are formed on the joining surfaces 24, 25of the silicon substrate 20. Metal, etched grooves, oxide films, or thelike are used to form these marks 41-1 through 41-4. On the joiningsurfaces 34, 35 on the back face of the PLC substrate 30 also, thirdpositioning marks 42-1 through 42-4 are formed, corresponding to thepositioning marks 41-1 through 41-4. Metal, quartz, or the like are usedto form these third positioning marks 42-1 through 42-4.

For mark image recognition, application of mark edge recognition methodsusing a white-light epi-illumination image, a red-light transmissiveimage or a reflected image, or of area-weighted methods is conceivable.Marks 41-1 through 41-4, 42-1 through 42-4 in four corners, or in twoopposing corners in strip shape, of the substrates 10, 20, 30 are formedwith high precision, and image recognition is used to perform three-axisadjustment of the angles and optical axes of the joining-surfacedirections, or of directions parallel to optical axes.

This fourth embodiment has the following advantageous results.

By simultaneously creating marks 41-1 to 41-4 and so on on the siliconsubstrates 10, 20 for positioning the light emitting element 18,photo-receiving element 19, optical fiber, and PLC substrate 30,mounting of each of these optical components with high-precisionpositioning is possible.

Fifth Embodiment

FIG. 8 is a diagram explaining a method of position alignment, showing afifth embodiment of this invention, which is an example of applicationof a mark edge recognition method. In this FIG. 8, the mark 41-1 on thesilicon substrate 10, and part of the mark 42-1 on the PLC substrate 30,are shown.

In this positioning method, by adjusting the distances A, B betweenedges of the marks 41-1, 42-1, and similarly for the marks 41-1, 42-1, .. . of all four corners or of two corners, three-axis adjustment similarto that of the fourth embodiment is possible, and an advantageous resultsimilar to that of the fourth embodiment is obtained.

Sixth Embodiment

FIG. 9 is a diagram explaining a method of position alignment, showing asixth embodiment of this invention, which is an example of applicationof a mark edge recognition method.

In FIG. 9, an example is shown in which etched grooves are used as themarks 41-1, . . . on the silicon substrates 10, 20. In order to absorbthe thickness of the mark or marks 42-1 formed on the PLC substrate 30(for example, the thickness of a metal mark, or the swelling of quartzdue to a mark), a construction is adopted in which the mark 42-1 of thePLC substrate 30 is superposed on the etched groove side of the marks41-1, . . . of the silicon substrates 10, 20.

This sixth embodiment has the following advantageous result.

The mark 42-1 on the PLC substrate 30 is superposed on the V groove markor marks 41-1 formed in the silicon substrates 10, 20, so that thethickness of the mark 42-1 on the PLC substrate 30 is absorbed.Consequently the mounting precision of the joining surfaces of thesilicon substrates 10, 20 and the PLC substrate 30 is not degraded, andno positional deviations occur in the heights of the optical axes ofeach of the optical components.

Seventh Embodiment

FIG. 10 is a diagram explaining a method of position alignment in aseventh embodiment of this invention, which is an example of theapplication of a mark edge recognition method.

In FIG. 10, similarly to FIG. 9, an example is shown of the use ofetched grooves, for example V grooves in an L shape, as the marks 41-1,. . . on the silicon substrates 10, 20. An aperture part 43-1 is formedin the end part of the etched groove of the mark 41-1, and an aperturepart 43-2 is also formed in the end part of the dicing groove 16. Theaperture part 43-1 is provided as an entrance for influx of adhesiveresin applied from the side faces of the silicon substrates 10, 20. Theaperture part 43-2 is an aperture to exude adhesive resin, and toprevent voids from remaining in the etched groove upon influx of theadhesive resin.

This seventh embodiment has the following advantageous result.

Because the aperture parts 43-1, 43-2 are provided as apertures forinflux and exuding of adhesive resin in the V groove mark 41-1 of thesilicon substrates 10, 20, the functions of a mark for positionadjustment and of a means for the smooth influx of adhesive resin can becombined.

In this invention, the positioning marks can be formed on a substratewith high precision. This is because the positioning marks and theoptical waveguide formed of glass are divided into separate substratesand formed using separate processes, so that a silicon substrate neednot be subjected to heat treatment in order to render glass transparent,so that defects do not occur in the silicon crystal. Further, in thisinvention it is possible to form positioning marks on substrates withoutusing mask members for application of metal material to the substrate;hence there is no shifting of a mask member position, nor is theredispersion of the metal material caused by a gap between a mask memberand the substrate.

In this invention, positioning marks and grooves can be formed in asingle process; as a result, positioning marks can be formed on asubstrate with high precision, and without shifts in position.

Examples of Variations of Embodiments

This invention is not limited to the above embodiments, and othervariations and embodiments are possible. Such variations or embodimentsmay, for example, include the following (1) and (2).

(1) In the first through third embodiments, examples of application tooptical waveguide transmitter-receiver modules used in STM-PON systems,π-PON systems, ATM-PON systems, and other systems were described; but byapplication to optical multiplexer/demultiplexer arrays employingoptical waveguides, and to connection of multi-core waveguides andoptical fibers, advantageous results similar to those of the aboveembodiments can be anticipated.

(2) By combining a plurality of silicon substrates 10, 20, . . . and PLCsubstrates 30, . . . , optical circuit configurations more complex thanthose of the above embodiments are possible. This method is not limitedto silicon substrates 10, 20, . . . and PLC substrates 30, . . . , butcan also be applied to join substrates of the same type, or to join flatsubstrates using other types of materials.

Specific configurations of these modules are explained using FIGS. 11through 17.

FIG. 11 shows a first variation.

The silicon substrate 10 is the first substrate. A fiber 52, cover 53,monitor photodiode 55, and laser diode 56 are mounted on the siliconsubstrate 10. A V-shape groove 54 for mounting of the fiber 52, firstpositioning marks 60-1 and 60-2, and a groove 11 are formed in thesilicon substrate 10. The groove 11 is provided so that the siliconsubstrate 10 does not interfere with the optical waveguide provided inthe PLC substrate 50; by this means, the junction of the siliconsubstrate 10 and the PLC substrate 50 is made smooth.

The silicon substrate 20 is the second substrate. A photodiode 57 ismounted on the silicon substrate 20. Second positioning marks 61-1 and61-2, and a groove 21, are formed in the silicon substrate 20. Thegroove 21 is provided in order that the silicon substrate 20 does notinterfere with the optical waveguide provided in the PLC substrate 50;by this means, the junction of the silicon substrate 20 and the PLCsubstrate 50 is made smooth.

The PLC substrate 50 is the third substrate. An optical waveguide isformed in the PLC substrate 50 and a slight protrusion is formed on theperiphery of the optical waveguide. Wavelength-division multiplexing(WDM) 59, which separates wavelengths, is mounted on the PLC substrate50. Third positioning marks 62-1 to 62-4 are formed on the PLC substrate50. The PLC substrate 50 is positioned above the silicon substrate 10such that the third positioning marks 62-1 and 62-2 are aligned with thefirst positioning marks 60-1 and 60-2, and the two substrates are bondedtogether; and the PLC substrate 50 is positioned above the siliconsubstrate 20 such that the third positioning marks 62-3 and 62-4 arealigned with the second positioning marks 61-1 and 61-2, and the twosubstrates are bonded together.

A ceramic substrate 51, which is a fourth substrate, is bonded to thebottom of the module formed by the silicon substrate 10, siliconsubstrate 20, and PLC substrate 50, to support these. The ceramicsubstrate 51 electrically insulates the silicon substrate 10, siliconsubstrate 20, and PLC substrate 50 from the outside, and providesprotection to prevent deformation of the silicon substrate 10, siliconsubstrate 20, and PLC substrate 50.

In the example shown in FIG. 11, a groove is provided in the top surfaceof the silicon substrates to prevent interference with the opticalwaveguide; but other constructions are possible. FIG. 12 shows anotherconstruction, and FIG. 13 shows still another construction. FIG. 12shows that protruding portions 63-1 and 63-2 are provided on the siliconsubstrate 10′ and the silicon substrate 20′. FIG. 13 shows thatprotruding portions 65-1 and 65-2 are provided on the PLC substrate 50′.

FIG. 14 shows a second variation.

FIG. 14 shows a configuration in which the first substrate and thesecond substrate are integrated.

A common substrate 70 is the result of integrating the first substrateand the second substrate. The common substrate 70 is bonded to the PLCsubstrate 71 above, and to the ceramic substrate 51 below.

FIG. 15 shows a third variation.

FIG. 15 shows a configuration in which fibers are mounted on the siliconsubstrates without mounting an optical element (emission element,receiving element).

On a silicon substrate 80, which is the first substrate, no opticalelements (emission element, receiving element) are mounted, but fibers83-1 and 83-2 are mounted. On silicon substrate 81, which is the secondsubstrate, no optical elements (emission element, receiving element) aremounted, but a fiber 84 is mounted.

FIG. 16 shows a fourth variation.

FIG. 16 shows a configuration in which the first substrate and secondsubstrate are integrated with fibers mounted, without mounting anyoptical elements (emission elements, receiving elements).

Fibers 92, 93-1, and 93-2 are mounted in common substrate 90 withoutmounting any optical elements (emission elements, receiving elements).FIG. 16 shows that the number of input members and the number of outputmembers can be modified arbitrarily.

FIG. 17 shows a fifth variation.

FIG. 17 shows a configuration in which a fiber array, obtained bybundling a plurality of fibers, is mounted on a common substrate.

On common substrate 100 are mounted a fiber array 102, obtained bybundling a plurality of fibers 103-1 to 103-4; a fiber array 104,obtained by bundling a plurality of fibers 105-1 and 105-2; and a PLCsubstrate 101. FIG. 17 shows that the number of input members and thenumber of output members can be changed to m×n.

1. An optical waveguide transmitter-receiver module, comprising: a firstsubstrate having a first positioning mark on a top surface side thereof;a second substrate having a second positioning mark on a top surfaceside thereof; a third substrate having an optical waveguide formedtherein, optical waveguide entry and exit end faces and a thirdpositioning mark on a bottom surface side thereof; wherein protrudingportions, which are formed on both top surfaces of said first and secondsubstrates or a bottom surface of said third substrate, have a flat topor bottom surface, respectively, for bonding with said bottom surface ofsaid third substrate or said both top surfaces of said first and secondsubstrates; said both top surfaces of said first and second substratesor said bottom surface of said third substrate is flat for bonding withsaid flat top or bottom surface of said protruding portions; each ofsaid first and second substrates and said third substrate are positionedtogether with reference to said first and second positioning marks andsaid third positioning mark, and bonded to each other at said flat topor bottom surface of said protruding portions so as to form at least onegap between each of said first and second substrates and said thirdsubstrate; a guide protruding portion formed on said bottom surface ofsaid third substrate; and a guide depression formed on said top surfaceof said first or second substrate; wherein said guide protruding portionis arranged at a position, which is different from a facing position tosaid protruding portions, and in a crossing direction with saidprotruding portions; and said guide depression is arranged to opposingsaid guide protruding portion.
 2. An optical waveguidetransmitter-receiver module, comprising: a lower-side substrate having atop surface-side positioning mark on a top surface side thereof andprotruding portions formed on a top surface thereof; an upper-sidesubstrate having an optical waveguide formed therein, optical waveguideentry and exit end faces and a bottom surface-side positioning mark on aflat bottom surface thereof; wherein said protruding portions have aflat top surface respectively for bonding with said flat bottom surfaceof said upper-side substrate; said lower-side and upper-side substratesare positioned together with reference to said top surface-sidepositioning mark and said bottom surface-side positioning mark, andbonded to each other at said flat top surface of said protrudingportions so as to form at least one gap between said lower-sidesubstrate and said upper-side substrate; a guide protruding portionformed on said flat bottom surface of said upper-side substrate; and aguide depression formed on said top surface of said lower-sidesubstrate; wherein said guide protruding portion is arranged at aposition, which is different from a facing position to said protrudingportions, and in a crossing direction with said protruding portions; andsaid guide depression is arranged to opposing said guide protrudingportion.
 3. An optical waveguide transmitter-receiver module,comprising: a lower-side substrate having a top surface-side positioningmark on a flat top surface thereof; an upper-side substrate having anoptical waveguide formed therein, optical waveguide entry and exit endfaces, a bottom surface-side positioning mark on a bottom surface sidethereof and protruding portions formed on a bottom surface thereof onthe periphery of said optical waveguide; wherein said protrudingportions have a flat bottom surface respectively for bonding with saidflat top surface of said lower-side substrate; said lower-side andupper-side substrates are positioned together with reference to said topsurface-side positioning mark and said bottom surface-side positioningmark, and bonded to each other at said flat bottom surface of saidprotruding portions so as to form at least one gap between saidlower-side substrate and said upper-side substrate; a guide protrudingportion formed on said bottom surface of said upper-side substrate; anda guide depression formed on said flat top surface of said lower-sidesubstrate; wherein said guide protruding portion is arranged at aposition, which is different from a facing position to said protrudingportions, and in a crossing direction with said protruding portions; andsaid guide depression is arranged to oppose said guide protrudingportion.